1. Technical Field of the Invention
The present invention relates to a cheese manufacturing method, particularly to a cheese manufacturing method in which a cheese yield is enhanced by elaborately utilizing a milk whey protein (hereinafter referred to simply as a whey protein), or the whey protein and transglutaminase (hereinafter abbreviated as TG)
2. Prior Art
It is considered that a cheese originated when human beings began to raise livestock, that is, around 6,000 B.C. Generally, the cheese is roughly classified into a processed cheese and a natural cheese. The natural cheese is classified into ripen cheeses such as a super-hard cheese, hard cheese, semi-hard cheese, and soft cheese, and fresh cheeses subjected to no ripening process.
The cheese is manufactured according to a very exquisite and sophisticated principle. First, manufacturing of the ripen natural cheese will be described.
Examples of a milk as a raw material (material milk) include milks of a cow, goat, sheep, buffalo, reindeer, donkey, camel, and the like, and these are used not only in a whole milk but also in a semi-skim milk, skim milk, and the like. As well known, a milk coagulating enzyme called chymosin (or rennet) is added to the material milk, or a so-called cheese starter, and the like are used, if necessary or as desired, in the material milk to form a coagulated material (cheese curd) (milk coagulating treatment). A major protein in the material milk is casein, and is formed of xcex1s1-, xcex1s2-, xcex2- and xcexa-casein. The casein forms a micelle structure and exists in the material milk. The xcexa-casein is distributed in the surface of a casein micelle, and contributes to stabilization of the micelle. Chymosin is an enzyme which cuts xcexa-casein by a specific site, and through the cutting, peptide (called glycomacropeptide (GMP)) on a C terminal end which is exposed on the surface of the casein micelle and which is highly hydrophilic is separated from xcexa-casein. GMP exists as a part of the whey protein after separated. After the cutting, remaining xcexa-casein is called para-xcexa-casein, and is highly hydrophobic peptide. Therefore, after chymosin acts on xcexa-casein, the highly hydrophobic para-xcexa-casein is distributed in the surface of the casein micelle, and the casein micelle becomes unstable. As a result, the casein coalesces, and forms a so-called cheese curd.
Subsequently, the cheese curd is finely cut, and a whey protein is separated (primary whey). Subsequently, the separated cheese curd is cleaned with a warm water, excessive lactose is removed and additionally the remaining whey protein is removed (secondary whey). Subsequently, the cheese curd is collected, and squeezed. After the curd is squeezed for a given time, salt is added to the curd. The curd is subjected to a ripening process, ripened for a given period, and formed into the natural cheese.
Additionally, as described above, the whey protein separated after the cheese curd is formed is a byproduct in the cheese manufacturing. The whey protein is mainly constituted of xcex2-lactoglobulin, xcex1-lactoalbumin, serum albumin, IgG and GMP. At present, a part of the whey protein is used for manufacturing various foods and for feeding animals. A high nutritive value of the whey protein has been known long (Barth and Behnke; Nahrung, vol. 41, pp. 2 to 21, 1997), and effective use of the whey is considered to be also industrially very advantageous.
Moreover, as described above, in the cheese manufacturing, casein in a solid content of the material milk excluding whey components (lactose, whey protein, and the like) is a main cheese constituting component, and all solid contents of the material milk do not form the cheese. Therefore, in the industrial manufacturing of the cheese, it goes without saying that it is desirable from viewpoints of costs and effective utilization of a milk resource to be able to manufacture as much cheese as possible from a constant amount of the material milk. Moreover, there is another advantage that a product can be supplied to a consumer inexpensively by establishing a high-yield cheese manufacturing method. However, for a conventional cheese manufacturing technique, under existing circumstances, it cannot necessarily be said that a yield of the cheese curd is high. Enhancement of the yield of the cheese curd means that a casein fraction coagulated through chymosin treatment is quantitatively increased. That is, it is a technical problem to incorporate much whey protein in the cheese curd during preparation of the cheese curd.
Attempts have been made to reduce the whey protein discharged into the whey as much as possible and enhance the yield of the cheese curd. For example, a method of concentrating a volume of the material milk to about ⅓ by ultrafiltration and using the material milk to manufacture the cheese is described in U.S. Pat. No. 4,205,090. PCT National Publication No. 501810/1982 describes a method of selectively concentrating the material milk by ultrafiltration to enhance an ion strength in the material milk, fermenting the material milk, removing water from the material milk, and using this raw material to manufacture the cheese. Furthermore, it is described in Japanese Patent Application Laid-Open No. 308756/1990 that when the whey secondarily produced during manufacturing of the cheese is concentrated, and the concentrated whey protein and concentrated material milk are used to manufacture the cheese, the obtained cheese curd contains a high concentration of the whey protein, and the whey protein as a resulting byproduct can effectively be utilized.
However, in these techniques, the material milk or the reused whey needs to be preprocessed by the ultrafiltration, and it is difficult to say that this is an industrially convenient method. Moreover, for the cheese manufacturing method in which the material milk treated by the ultrafiltration is used, it is known that with a short-term ripened cheese, a product quality is not affected. However, with a long-term ripened cheese, protein decomposition or cheese flavor generation is sometimes inhibited. This may supposedly be explained from facts that in the cheese rich in an unmodified whey protein the whey protein itself is not easily decomposed and the whey protein inhibits decomposition of casein by protease (Jameson and Lelierve; Bulletin of the IDF, vol. 313, pp. 3 to 8, 1996, deKoning et al.; Neth. Milk Dairy Journal, vol. 35, pp. 35 to 46, 1981, Bech; International Dairy Journal, vol. 3, pp. 329 to 342, 1993). In conclusion, it cannot be said that the existing cheese manufacturing technique by concentration of the material milk sufficiently satisfies the consumer in quality implications such as a flavor and texture.
In order to enhance the yield of the cheese curd, it is a technical problem to effectively incorporate the whey protein discharged in the whey into the coagulated casein by rennet treatment (coagulating treatment), that is, into the cheese curd, which has been described above. As one example of solution means of this problem, transglutaminase (TG) as a protein crosslinking enzyme is utilized. As well known, TG is an enzyme which catalyzes acyl transition reaction between xcex3-carboxyamide group of a remaining glutamine group in the protein and various first-class amines. When the first-class amine is an xcex5-amino group of lysine, an xcex5-(xcex3-glutamil)lysine crosslink is formed among a protein or polypeptide chain, and this crosslink can form a protein crosslinked polymer.
These days, TG has been used for manufacturing many foods such as a marine product made with a boiled fish paste, and a processed livestock product. Moreover, an example in which TG is also used in a dairy product has been reported. For example, in Japanese Patent Application Laid-Open No. 27471/1989, a cheese manufacturing method including a process of adding TG in a manufacturing process is described. However, in the described cheese manufacturing method, the cheese is manufactured from the curd formed using gluconodeltalactone and TG, or only TG without using rennet. This is different from the aforementioned cheese basic manufacturing principle. Moreover, in Japanese Patent Application Laid-Open No. 131537/1990, a method of using TG to manufacture a cheese food is described, but the cheese food as an object herein is manufactured by heating/melting the natural cheese or the processed cheese as the raw material. This is far different from the viewpoint of the cheese curd yield enhancement targeted by the present invention. In publication WO94-21129, a method of adding TG to the milk to manufacture a gel for an acid food is described. However, in this method, no rennet is added, and an object of the method is to manufacture a dairy product having an innovative texture without using emulsifier or stabilizer. Therefore, the viewpoint of the yield enhancement according to the present invention is not described in the publication.
Of course, the cheese manufacturing method using TG and rennet is described in the publication WO94-21130. However, different from a usual cheese manufacturing method, separation of the cheese curd from the whey is not described, and this method is far different from the cheese manufacturing method including the whey separation as the object of the present invention. Moreover, the yield enhancement is not described. Furthermore, in a publication EP0711504, a technique of treating a material milk with TG, heating and deactivating TG, adding rennet, and manufacturing the cheese is described. It is also described that the yield of the cheese curd can be enhanced. However, this cheese manufacturing method starts from the material milk itself. This is different from a method of adding/mixing a whey protein treated by a protein decomposing enzyme to the material milk, and subjecting this mixture directly to a milk coagulating treatment, or allowing TG to act on the mixture and subsequently subjecting the mixture to the milk coagulating treatment according to the present invention.
Additionally, as described above, some ideas that the whey protein is utilized to enhance the cheese yield have been reported. Moreover, some techniques of utilizing TG to manufacture the dairy product have also been reported. As described later, the present invention is based on an idea that the whey protein is incorporated into the cheese curd by transforming the whey protein to a partial hydrolysate, or by using the whey protein transformed into the partial hydrolysate together with TG.
Additionally, it is inherently known that the whey protein itself cannot easily undergo action of TG. This is supposedly because xcex2-lactoglobulin, xcex1-lactoalbumin, and serum albumin as the main components of the whey protein are all globular proteins having many disulfide bonds in molecules. The disulfide bond is a covalent bond, and is a remarkably stable bond. That is, the whey protein can be said to be a very stable globular protein which does not easily cause a structure change. In other words, as a cause why the whey protein does not easily undergo the TG action, a residual glutamine group or a residual lysine group necessary for undergoing the action is not distributed in the surface of the whey protein, and the protein cannot participate in crosslinking reaction. Alternatively, there is supposedly a situation in which a firm globular structure prevents the protein from easily contacting the enzyme. In fact, except the whey protein, for example, for actin as a muscle structure protein which is another globular protein, it is also remarkably difficult to undergo the TG action. From these facts, it cannot but be said that it is remarkably difficult to utilize TG and incorporate the whey protein into the cheese curd.
Additionally, an attempt to treat the protein with protease and allow TG to act on the protein has already been reported (Babiker et al.; Journal of Agricultural and Food Chemistry, vol. 44, pp. 3746 to 3750, 1996). It is also described that gluten as a wheat protein is treated with protease, TG is allowed to act on the protein, and gluten functional properties such as an emulsifiable property and bubbling property can be enhanced. Moreover, in Japanese Patent Application Laid-Open No. 126039/1992, a technique is described in which a bitter taste generated by the protease treatment can be reduced by TG treatment. However, these techniques are far different from the present invention whose object is to enhance the action of TG to the whey protein, also enhance the yield of the cheese curd, and finally enhance the cheese yield.
Additionally, a publication WO91-13553 discloses a technique of adding protease directly to the material milk, adding a material obtained by specifically hydrolyzing only the whey protein to another material milk, and using this material to manufacture the cheese. As described above, it is known that addition of an excessive whey protein inhibits generation of a flavor of the ripened cheese in the manufacturing of the natural cheese. An object of the technique disclosed in the WO91-13553 is to prevent this. This is far different in object and embodiment from the present invention in that there is no viewpoint of the yield enhancement and protease is added directly to the material milk in a mixed state of the whey protein and casein.
[Problem to be Solved by the Invention]
Under background of the aforementioned prior art, an object of the present invention is to provide a method for enhancing a yield of a cheese curd from a material milk and a yield of a cheese, and manufacturing a cheese superior also in quality.
[Means to Solve the Problems]
The present inventor has intensively studied enhancement of a yield of a cheese curd in cheese manufacturing in order to effectively utilize a milk resource. As a result, it has been found that an incorporated amount of a whey protein into the cheese curd is increased by elaborately using the whey protein during manufacturing of a cheese, or by elaborately using the whey protein and TG, and this achieves curd yield enhancement. The present invention has been completed based on such finding.
Accordingly, the present invention relates to a cheese yield enhancing method in a cheese manufacturing method including a process of separating a cheese curd from a whey after a milk coagulating treatment of a material milk by a milk coagulating enzyme, said cheese yield enhancing method comprising steps of: adding/mixing a protein decomposing enzyme treated material of a milk whey protein (a partial hydrolysate of the milk whey protein) to the material milk; and subjecting a resulting mixture to the milk coagulating treatment by the milk coagulating enzyme, and also to a cheese yield enhancing method in a cheese manufacturing method including a process of separating a cheese curd from a whey after a milk coagulating treatment of a material milk by a milk coagulating enzyme, said cheese yield enhancing method comprising steps of: adding/mixing a partial hydrolysate of a milk whey protein to the material milk; allowing transglutaminase to act on a resulting mixture; and subjecting the mixture to the milk coagulating treatment by the milk coagulating enzyme.